SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b26dd0fb5435f4206f944516bb6ea139c9c3c74079001eacacb4f2d0b0b99933' 
  AND token = 'PuiiVhfzIOsAxg+HwDYFZVJbbMnAFa8/kogjTuaqWZA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}